Characterization of adsorption and reduction of noble metal ions by bacteria

The biomass D01 was screened from the soil of mining area and it was identi fied as Bacillus megatherium. It is able to adsorb and reduce the noble met al ions such as Pd2+, Au3+ and Ag+ etc. at room temperature. At pH 3. 5, th e adsorbed ratio were 93.2%, 99.5% and 98.1.%, respectively within 2 h. In situ TEM images showed that the Au, Ag particles adsorbed on the cell wall grew up gradually, Some of the Au particles formed polyhedron particles, wh ile some ones broke off from the cell. The particle size can be controlled to be several nano-meters to more than a hundred nano-meters, XPS and XRD r esults indicated that Au3+, Ag+ and Pd2+ could be reduce to metals much fas ter than Rh3+ and Pt4+ by D01, Peaks at. 3 087 and 1 664 cm(-1) in the IR s pectra of D01 reduced gradually while interacting with metal ions, implying that metal ions were coordinated and reduced on the site of acylamide of D 01. This is a promising method for preparation of metal catalysts with high dispersion and nano-meter sized metal particles.